This invention relates to a method and apparatus for preventing the copying of a video program. More particularly, it relates to modifying a video signal in a manner detectable by a video recorder apparatus and disabling the recording device when the modified video signal is detected.
Various apparatus and methods have been developed for modifying a video signal so that a normal color picture may be produced by a television receiver receiving the modified video signal, but that video recording of the modified video signal is impaired. That is, a video picture produced from the video signal as recorded on a video tape recorder is altered so that it makes unacceptable viewing.
U.S. patent application Ser. No. 724,006, filed in the U.S. Patent and Trademark Office on Apr. 17, 1985 and entitled "Method and Apparatus for Processing a Video Signal so as to Prohibit the Making of Acceptable Video Tape Recordings Thereof" (now U.S. Pat. No. 4,631,603), which is incorporated herein by reference, discloses such a method and apparatus. It describes adding ordered pairs of pseudo-sync pulses and white pulses during the vertical blanking interval. These pulse pairs act in concert to confuse the automatic gain control system of a video cassette recorder (VCR), leading to generally unviewable pictures.
As VCR's become more sophisticated, such as including dubbing (integrated playback and recording) systems, the likelihood of copying video tapes increases. Present systems do not prevent the copying of video tapes, but rather produce modified video tape signals which, when recorded by a VCR and played back, produce impaired pictures It is desirable to prevent the taping of video signals altogether.